text: On the opposite extreme, the central carbon–carbon single bond of diacetylene is very strong at 160 kcal/mol, as the single bond joins two carbons of sp hybridization. Carbon–carbon multiple bonds are generally stronger; the double bond of ethylene and triple bond of acetylene have been determined to have bond dissociation energies of 174 and 230 kcal/mol, respectively. A very short triple bond of 115 pm has been observed for the iodonium species [HC≡C–IPh] [CFSO], due to the strongly electron-withdrawing iodonium moiety.